Thesis (MSc. (Physics)) --University of Limpopo, 2015 / This study investigated the extent to which learners from rural and peri-urban areas understand what the symbols represent and their roles in simple direct current resistive electrical circuits. The emphasis was on simple direct current resistive electrical circuits that consist of batteries and bulbs. The study was carried out with Grade 12 learners at high school level in the Limpopo Provincial Department of Education. It used both qualitative and quantitative data collection methods to investigate learners’ understanding of direct current resistive electrical circuits at rural and peri-urban schools. It used questionnaires and structured interviews to collect the data so that the results could provide in-depth understanding and generalizability. The results revealed that learners knew the symbols used in direct current resistive circuits, however, when the circuit was populated with a number of known symbols it became complex to such an extent that some learners struggled to identify the symbols. As it appeared, learners could not conceptualize the role played by a battery, conductor, ammeter and voltmeter in direct current resistive electrical circuit. In addition, the study also revealed that learners experience difficulties when translating a real circuit to a schematic circuit. This study suggests that deeper focus has to be directed towards developing leaners’ understanding of the working and role played by each symbol in a schematic circuit. Learners were operating at far lower conceptual basis and thought of conductor as a hollow pipe like material. Results were also compared in terms of geographical location of the school, and findings indicate that the rural school was performing better than peri-urban school. The results highlight a number of the frequently encountered alternative frameworks which learners come across when they are faced with schematic circuit diagrams. Most of the alternative frameworks found are well documented in literature (for example current consumption, difficulty with understanding electric concepts, difficulty with concept differentiation, and no firm alternative frameworks). vi The participants in this study were not exposed to practical work. This suggests the results might be different with learners exposed to practical work. It is therefore recommended that future studies look at the understanding of the role played by individual electrical components with learners who had practical experience with real electrical circuits. Majority of learners in this study could not communicate their scientific conclusions using English, as the English is their second language.

This thesis describes the design of a baseband digital predistortion architecture for radio frequency (RF) amplifier linearization. Existing amplifier linearization techniques are first examined. The nonlinearity of an amplifier can be characterized as amplitude-to-amplitude distortion and amplitude-to-phase distortion. The distortion can be corrected by providing a predistorted driver signal (both in amplitude and phase) to the amplifier. This counteracts the nonlinearity of the amplifier so that the overall system is more linear. A pipelined predistortion architecture is designed to allow fast processing speed, and is capable of providing linearization for a bandwidth of 25 Mhz. The simulation results show significant improvement in amplifier's performance using predistortion technique. The system bandwidth versus cost is examined by using commercially available components. / Graduation date: 1996

Thesis (M.S.)--Brigham Young University. Dept. of Electrical and Computer Engineering, 2004. / Includes bibliographical references (p. 71-72).

published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

No description available.

In this thesis the ANTICS analogue fault simulation software is described which provides a statistical approach to fault simulation for accurate analogue IC test evaluation. The traditional figure of fault coverage is replaced by the average probability of fault detection. This is later refined by considering the probability of fault occurrence to generate a more realistic, weighted test metric. Two techniques to reduce the fault simulation time are described, both of which show large reductions in simulation time with little loss of accuracy. The final section of the thesis presents an accurate comparison of three test techniques and an evaluation of dynamic supply current monitoring. An increase in fault detection for dynamic supply current monitoring is obtained by removing the DC component of the supply current prior to measurement.

The recently developed gate turn-off thyristor is now becoming well established as the first choice switching device in high power converters for applications such as uninterruptible power supplies, frequency changers, and AC and some DC variable speed motor drives. The special operating features of these devices in conventional circuit configurations are investigated. The GTO thyristor physical behaviour and operating characteristics are first described and supported by measurements made at turn-off currents of up to 600A on a specially constructed test circuit. From this, it is shown that, owing to the extremely fast rates of fall of anode current at turn-off, voltage overshoot effects caused by the stray circuit inductances are highly dangerous to the device, and effective snubbing is essential. A detailed study of these stray inductance effects in constructed DC chopper and H-bridge inverter circuits follows. The circuits are modelled to include these strays, with appropriate mathematical analysis and computer simulation, to determine which stray inductances are the most influential in causing GTO thyristor voltage stress. The different switching patterns are considered for the H-bridge to provide quasi-square and various pulse width modulated (PWM) output voltage waveforms, and the detailed current transfer paths in the various circuit devices and snubber components defined and mathematically analysed in each case. Practical switching effects of diode reverse recovery and GTO mismatched switching times are demonstrated and possible damaging conditions revealed. All analytical and computed results are supported by experimental measurements. A GTO thyristor will be damaged by attempting to turn-off an over-current, and satisfactory protection against this is essential. Conventional fusing is usually inadequate, and a better method is to use a fast active system utilising either a crowbar and fuse, or rapid direct gate turn-off. Both methods are investigated and experimental results provided. It is concluded that, with appropriate circuit layout and component choice, the unavoidable stray inductance effects can be limited to manageable levels. The most severe effects are caused by the DC source inductance which is the most difficult to minimise. Others within the power circuit, if kept small, will have a marginal effect. Fast over-current protection is achievable

Thesis (Ph. D.)--Ohio University, November, 1994. / Title from PDF t.p.

Thesis (Ph. D.)--Ohio University, March, 1999. / Title from PDF t.p.

Thesis (Ph. D.)--Carleton University, 2004. / Includes bibliographical references (p. 156-176). Also available in electronic format on the Internet.